disconnect vs undo

disconnect is a noun but undo is not a noun.

Word	Noun	Adjective	Verb	Adverb
disconnect	Yes	No	Yes	No
undo	No	No	Yes	No

As verbs, undo is a hypernym of disconnect; that is, undo is a word with a broader meaning than disconnect:

disconnect (noun)	undo (noun)
an unbridgeable disparity (as from a failure of understanding)

disconnect (verb)	undo (verb)
make disconnected, disjoin or unfasten	cancel, annul, or reverse an action or its effect
pull the plug of (electrical appliances) and render inoperable	cause to become loose
	remove the outer cover or wrapping of
	deprive of certain characteristics
	cause the ruin or downfall of